Advances in technology have led to the development of miniature medical devices that can be implanted within a living organism, such as a human, to provide treatment or monitoring. Powering such implantable medical devices can be a concern. For example, some implantable medical devices use an onboard battery as a power source. However, since batteries store a finite amount of energy, an onboard battery may only be a temporary power source. Replacing batteries for implantable medical devices may be expensive and inconvenient. For example, depending on the specific nature of the implantable medical device, surgery may be needed to replace the device or to replace the battery.
Due to these and other concerns, some implantable medical devices may use rechargeable batteries. However, recharging batteries that are located inside a device that is implanted in a patient presents other concerns. For example, when long charging times are required, patient compliance can be a problem. As another example, inefficient recharging may cause energy to be lost as heat. Such heat losses may dissipate into surrounding tissues, which may be harmful to the patient.